With Rick Santorum out of the picture and the general election between Mitt Romney and Barack Obama all but sealed, now is a good time to reflect back on the Republican primary, one which truly revealed the complex relationships that can exist between campaigns. The momentum of a strong victory in one state propelled a candidate forward in the weeks and months ahead, while weaker candidates were pushed aside by their heftier opponents time and time again. In John Donne’s words, “No man is an island, entire of itself.”

But for the past few months it has been difficult to follow the race without noticing the various unpredictable twists and turns that it took. There must have been more to it than four men and their political will, caught in a yearlong struggle to gain the Republican nomination.

In reality, the existence of a fifth candidate – whose influence changed the tides of victory and failure more than any individual – may explain this primary field’s volatility. The fifth candidate was outside money.

Millions in independent expenditure dollars flooded this primary battle in amounts never before seen in American history. This money, which cannot legally be tied to any one campaign, floated as a political goliath in the background of any caucus prediction and primary projection. The interactions between Mitt Romney, Newt Gingrich, Rick Santorum, Ron Paul, and Money made this an interesting five-person race to follow. Each candidate carried as much importance as the next.

Undoubtedly, outside money helped Mitt Romney the most. According to the Center for Responsive Politics, the Super PAC backing the Romney campaign spent more than $35 million on the primary cycle. Newt Gingrich was next in line with $16.2 million. Santorum’s received $6 million in outside assistance while Paul came in last with $3 million, each from their top respective independent expenditure committees. (Many candidates had more than one group supporting them.)

It is important to note that while each independent expenditure committee was associated with a candidate, there is nothing binding any PAC to a specific campaign. That they are, in fact and name, independent is an often under-reported aspect of independent expenditure committees. In fact, many big-time donors often gave to multiple PACs. Harold Simmons, the largest individual donor in this primary, gave a million dollars in indirect support for Rick Perry, another million to Newt Gingrich, $100,000 to Mitt Romney-affiliated groups, and $12 million to American Crossroads, Karl Rove’s brainchild.

Aside from being legally prohibited from coordinating with campaigns, these entities displayed an effect much larger than the campaigning or fundraising abilities of any candidate by himself. Romney’s victory in Florida, seen as a major turning point in his campaign, was fueled by $10.7 million in spending by his Super PAC. This vastly overtook spending for Gingrich, Santorum, and Paul combined. Most of the outside spending in Florida was on advertisements, and Floridians experienced first hand the saturation of TV and radio markets by outside spending. Independent expenditures spent almost $19 million in Florida, and they spent it almost exclusively on media (Super PACs, by their nature, have little else to spend money on). To put that in context, the Romney campaign itself spent $20.5 milliontotal on media over the course of the primary. Ron Paul’s campaign spent $9.9 million, Newt Gingrich’s campaign spent $5 million, and Rick Santorum’s campaign spent $3.5 million.

This means that the total Super PAC spending for one state (albeit a costly one) equaled around half of what the four official campaigns used on media for the entire primary. In other words, if TV advertisements are one of the main drivers of political influence, it could be easily argued that outside money influenced this primary as much as any one campaign did by itself. We may have strayed from a political environment in which a candidate with a clear message and a motivated base can win without the assistance of millions of outside dollars.

Money shaped this primary in unprecedented ways, and as we begin the general election season we will see a concentration of outside money that only intensifies these primary effects. In a field of five, money played an important role, and in lead up to November 6th, it will truly create one mammoth of a third candidate, able to influence our next president in unimaginable ways.